The present invention provides an amorphous, pharmaceutically active form of a compound of formula I 
which is substantially free of crystalline compound. This compound is also known as 3-(1-methyl-3-indolyl)-4-(1-methyl-6-nitro-3-indolyl)-1H-pyrrole-2,5,-dione. This invention also provides a process for making the, amorphous form of the compound of formula I as well as pharmaceutical compositions including such compound.
A crystalline form of the compound of formula I is known. See, e.g., U.S. Pat. No. Re. 36,736. This crystalline form has a melting point of approximately 285xc2x0 C. (Id. column 22, lines 5-6). This compound belongs to a novel class of cell cycle inhibitors and apoptosis-inducers having potent anti-cancer therapeutic activity, in particular in solid tumors such as non-small cell lung, breast and colorectal cancers. See, e.g. U.S. Pat. No. 6,048,887 and EP 0 988,863. In its previously known crystalline form, compound of formula I has relatively low aqueous solubility ( less than 10 xcexcg/mL) at physiological pHs (which range from 1.5-8.0) and consequently less than optimal bioavailability (less than 5% in dogs). As this is a therapeutically active compound, it is thus desirable to obtain a form of the compound of formula I which has improved solubility/dissolution rate and bioavailability.
The bioavailability of a therapeutically active compound is generally determined by (i) the solubility/dissolution rate of the compound, and (ii) the partition coefficient/permeability of the compound through a subject""s gastrointestinal membrane. The major cause of poor bioavailability of a therapeutically active compound is usually the poor solubility/dissolution rate of said compound. Poor bioavailability is also often accompanied by high variable patient blood levels and unpredictable dose/therapeutic effects due to erratic absorption of the drug by the patient.
Several techniques can be used to improve the bioavailability of therapeutically active compounds having relatively low aqueous solubility. These techniques are discussed in the background Section of EP 0988,863. Also described in EP 0988,863, is a novel process pursuant to which crystalline therapeutically active compounds having relatively low aqueous solubilities may be rendered more bioavailable by being incorporated or dispersed in an ionic polymer.
While the dispersion or incorporation of therapeutically active compounds having relatively low aqueous solubilities in ionic polymers using certain methods may increase the bioavailability of these compounds, these methods can be cumbersome and time consuming. Such methods also require that the therapeutically active compounds are delivered to a patient in combination with a polymer, which may not always be beneficial or desirable. It is thus desirable to develop a process of making the compound of formula I in its amorphous form which does not require dispersion of the compound in a polymer.
The invention relates to an amorphous form of the compound of formula I which is substantially free of the crystalline form of the compound. This amorphous (also referred to as xe2x80x9chigh energyxe2x80x9d) form of the compound of formula I exhibits a faster dissolution rate than and superior bioavailability to the previously known crystalline form of the compound. The bioavailability of the amorphous form of the compound of this invention is significantly higher than the crystalline form of the compound, thereby enabling the amorphous form of the compound to be used in the treatment or therapy of cancerous tumors.
Another aspect of the invention relates to stable, amorphous compound of formula I which remains in stable, amorphous form for a period of time to permit the compound to have a reasonable shelf life (for example, two (2) years at room temperature) independent of form stabilizers such as an ionic polymer.
Another aspect of the invention is a process for making the high energy amorphous compound of formula I.
Another aspect of the invention is a pharmaceutical composition including a therapeutically effective amount of the compound of formula I in amorphous form.